Deciphering Bacteria’s Defenses, One Gene at a Time

To further complicate things, sporulation itself is not a straightforward, sequential process. While the genes do turn on in a step-wise, biblical “X begets Y begets Z” manner, the effect that the genes have is not that simple. A study (pdf) published in the Journal of Bacteriology last year showed how a series of consecutively activated genes modify the forming spore coat in opposing ways. It is similar to putting more than enough icing on the first layer in a cake, only to then wipe some of the icing off to achieve the ideal, intended coating before moving on to the next layer.

“We were surprised by this level of fine-tuning in the sporulation process,” says Lee Kroos, an author of the paper and a professor of biochemistry and molecular biology at Michigan State University in East Lansing. But despite this observed specificity, the paper also showed that B. subtilis can tolerate suboptimal situations—even if some of the genes in the sequence are “skipped” or de-emphasized, the spore coat can still turn out just fine. “It’s a remarkably robust system,” adds Kroos.

Enlightening Evidence

The lab work at NYU carries on: After centrifuging the spores in a beaker to obtain a nice, sample-ready clump of B. subtilis, Eichenberger or a team member prepares a slide and then heads to the microscopy room. By applying special illuminators, researchers can make the fluorescent dyes in the microbe’s proteins light up like glow sticks at a jam-band concert. A mini-camera then snaps some shots of the glowing germs, and with that, the two-day experiment is over.

Often, particular strains are preserved for future lab inquiry in a bureau-like freezer that has drawers full of mutated B. subtilis. Nearby, a growing chamber agitates more microbes in a nutrient solution for the next round of tests. Life is good right now for the feasting little guys, and in accordance, they emit a powerful reek.

“The smell gets pretty nasty sometimes,” Eichenberger admits, still not quite accustomed after years of manipulating the microorganisms.

This mild annoyance, however, isn’t all that bad when compared to the life-threatening traits of anthrax, B. subtilis’ close relative. As Eichenberger continues to decipher sporulation, and eventually the entire life cycle of B. subtilis gene-by-gene, perhaps he will unveil the origin of this milder form of nastiness as well.

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